A government-sanctioned conference of Roman Catholic delegates opened in Beijing today against a background of strife between China and the Vatican.

Ucanews, a missionary news service close to the Vatican, reported that several bishops and priests were being forced to attend the meeting, which the Holy See fears will be manipulated by the Chinese leadership.

It said yesterday police and government officials broke into the house of the bishop of Hengshui, in north-east China, where they became involved in "physical conflicts" with nuns and lay people attempting to protect the prelate, Peter Feng Xinmao. His home was surrounded by police cars, the agency said. Those inside were reciting rosaries.

Hengshui government officials said they had not heard of the matter. Police in the area could not be reached for comment.

Another bishop, also from Hebei province, was unreachable, while a third had been missing since he and seven others took part in a bishop's ordination opposed by the Vatican, Ucanews said.

The ceremony, at Chengde on 20 November, plunged relations between the Holy See and Beijing into crisis after several years of apparent convergence.

In 2007, Pope Benedict broke new ground when he declared the "underground" community, which answers to Rome, should reconcile with China's government-backed Chinese Catholic Patriotic Association (CCPA).

The ordination of Guo Jincai, a member of the Chinese parliament and former vice-secretary general of the CCPA, is thought to have been the first since then not to have been informally sanctioned by the Vatican.

The Holy See said the bishops who took part in the ordination had been coerced – a claim denied by the Chinese authorities. Cardinal Joseph Zen Ze-kiun, one of the pope's closest advisers on China, has since criticised the bishops.

In an article for Ucanews, he wrote: "The fact is that they did participate in the illicit ordination. They did impose their hands, however grudgingly. They did concelebrate."

Ren Yanli, who until 2005 led the Christian Studies section at the Chinese Academy of Social Sciences, said he believed the ordination of Father Guo reflected "an extreme left line in the government".

Dr Anthony Lam of the Holy Spirit Study Centre in Hong Kong said: "I think it's basically the strategy of a lower and middle level of cadres who want to control the church people, especially in Hebei. It may not be the strategy from the central government."

A Chinese expert, who asked not to be named because of the sensitivity of the issue, said: "The leadership of the patriotic church will be changed at the conference. The Vatican side hopes to use this as an opportunity to make some changes and have a sort of reform. Of course, the Chinese side doesn't want this to happen, so the conflicts between the two sides have intensified."

The vice-chairman of the CCPA said he had no time to comment. China's Religious Affairs Bureau did not respond to faxed queries. A spokesman for Beijing's foreign ministry said this month that the Vatican's criticism of Guo's ordination amounted to a violation of freedom of religion in China.

There are estimated to be at least 12 million Catholics in China. The communist authorities are wary of alternative organisations, and religions have been controlled by the state since the party came to power in 1949. Beijing and the Vatican cut ties two years later.

Some Chinese Catholics reject normalised relations because of their treatment by the state, and one observer said the pope's 2007 letter created three communities: the official, the "underground", and a self-styled "loyal church" of people unwilling to reconcile.